for people smart in science?

Question

what is a lever

Answer 1

A machine whereby a force applied at one point (the effort), acting around a pivot (fulcrum), acts on a force at a second point (the load).
The law of the lever says that the sum of moments of forces must be zero:
F1*d1 + F2*d2 = 0

Usually you want F2>F1, thus the point where you apply the force (p1) is further from the fulcrum than the second point (p2), i.e. d1>d2.

Points p1 and p2 can be either opposite sides relative to the fulcrum (e.g. a seesaw), or the same side (e.g. a nutcracker).

For many more examples: http://en.wikipedia.org/wiki/Lever

Answer 2

A lever is half of a simple machine known as a "lever and fulcrum." Technically, if you use the "see saw" example, the lever is the board you sit on. The "fulcrum" is the structure the lever rests on and pivots on.

A fulcrum and lever are "force multipliers." For example, take an 10 foot long 2X4 lever. Place a fulcrum under it 1 foot from the "lifting" end. Pushing down on the other end (nine feet from the fulcrum) with 1 pound of force will give you 9 pounds of lift.

Answer 3

In physics, a lever (from Old French levier, the agent noun to lever "to raise", c. f. levant) is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object. This is also termed mechanical advantage, and is one example of the principle of moments. The principle of leverage can also be derived using Newton's laws of motion, and modern statics. It is important to notice that the amount of work done is given by force times distance. The lever allows less effort to be expended to move an object a greater distance. For instance, to use a lever to lift a certain unit of weight with an effort of half a unit, the distance from the fulcrum of the spot where force is applied must be twice the distance between the weight and the fulcrum. For example, to halve the effort of lifting a weight resting 1 meter from the fulcrum, we would need to apply force 2 meters from the other side of the fulcrum. The amount of work done is always the same and independent of the dimensions of the lever (in an ideal lever). The lever only allows to trade effort for distance.


The three classes of levers
First-class levers
Second-class levers
Third-class levers




The three classes of levers
There are three classes of levers representing variations in the location of the fulcrum and the input and output forces.

First-class levers

A first-class lever is a lever in which the fulcrum is located in between the input force and the output force. In operation, a force is applied (by pulling or pushing) to a section of the bar, which causes the lever to swing about the fulcrum, overcoming the resistance force on the opposite side.


Examples:

Seesaw
Crowbar or claw hammer (removing nails)
Pliers
Scissors

Wheel and axle because the wheel's motions follows the fulcrum, load arm, and effort arm principle
Trebuchet an upside down example of the above picture
Oars, when used for rowing, steering, or sculling
Can opener and bottle opener
Bicycle hand brakes
Hand trucks are L-shaped but works on the same principle on the wheel as a fulcrum


Second-class levers



In a second-class lever the input is located to the far side of the bar, the output is located in the middle of the bar, and the fulcrum is located on the side of the bar opposite to the input. Examples:

Wheelbarrow
Nutcracker
Door
Pry bar
Stapler
Diving board
Wrench
Hand truck




Third-class levers

It is to be noted that for this class of levers, the input effort is higher than the output load, which is different from the first-class and second-class levers. However, also notice that the input effort moves through a shorter distance than the output load. Thus it still has its uses in making certain tasks easier to do.

Examples:

Human arm
Tweezers
Slings, trebuchets, and fishing rods (also spoons, when used for flinging food. This uses your index finger as the fulcrum, your thumb as the effort, and the load is the food.)
Any number of tools, such as a hoe or scythe
The main body of a pair of nail clippers, in which the handle exerts the incoming force
A baseball bat
A staple remover

Answer 4

A lever is a (usually simple) machine that makes the necessary required force to move one or more objects less (than before).
Examples include all types of wrenches.

Answer 5

A seesaw.

Answer 6

im not that smart but ... i think it's a handle or switch for something.

Answer 7

that stuff was there wen i was in 6th.4gotten all of it.